1. Field of the Invention
The present invention relates, in general, to watthour meters and, more specifically, to watthour meter socket adapters mountable in a watthour meter socket and receiving a watthour meter.
2. Description of the Art
In the electric utility industry, plug-in, socket-type watthour meters are commonly used to measure electric power consumption at residential or commercial sites. A socket housing is mounted on a convenient wall surface of the residence or commercial building and contains pairs of line and load terminals which are respectively connected to electric line conductors from the electric utility power network and load conductors which extend from the socket housing to the power distribution network in the residence or commercial building. The terminals receive blade contacts of a plug-in watthour meter to complete an electric circuit through the watthour meter between the line and load terminals.
In a three phase, three wire, delta connected utility power network, the pair of line jaw terminals and the pair of load jaw terminals in the socket receive the corresponding line and load blade terminals of a watthour meter. Such a watthour meter includes current elements which measure the combined power through the pairs of line and load terminals. It is assumed that all of the power supplied through the two pair of line and load terminals and the conductors connected thereto returns through the center or third conductor of the utility network which is typically unmeasured by the watthour meter. Thus, the third or center line conductor and center load conductor are merely connected together by a connector mounted on a standoff in the socket.
However, it has been found that in some installations by merely connecting a load between ground and the third or center load conductor, unmetered power may be taken from the load distribution network. In an attempt to address this problem, Ekstrom Industries, Inc., the assignee of the present invention, previously devised a watthour meter socket adapter formed of a interconnected base and shell which had a pair of line jaw terminals and a pair of load jaw terminals mounted therein. The pairs of line and load jaw terminals extend from a jaw terminal end mounted in the shell through the base and extend outward in the form of blade terminals for removable insertion into the jaw terminals in the socket. Folded over jaw terminals were mounted in the shell at the ninth and tenth terminal positions. Lugs were connected to the folded over jaw terminals for receiving the third line conductor and the third load conductor, respectively, after such third line and load conductors were passed through apertures formed in the base and shell of the adapter.
A splice connection was required to be made to the third line and load conductors in the socket after such third line and load conductors were disconnected from the center standoff to provide a suitable length of wire to pass through the apertures in the base and shell and to extend to a connection with the lugs in the shell of the adapter. A line jaw terminal mounted in the standard 5A terminal position in the base which provided the watthour meter with a proper voltage level was disconnected in the socket from the third line jaw and then connected to the socket ground aligned with the jaw terminal in the seventh terminal position in the shell. Then, a separate jumper was passed through the shell and connected between the jaw terminal at the standard seventh terminal position in the shell and the blade terminal at the 5A terminal position in the base and socket.
These connections were necessary in order to mount a watthour meter in the socket adapter which includes an additional current element and a pair of blade terminals connected thereto for measuring power drawn through the center or third line and load conductors. However, extensive modification was required to the socket adapter in order to form the apertures in the base and shell of the adapter for passage of the jumper and splice connections therethrough. In addition, a splice connection was required to provide a sufficient length of conductor to connect the center line and load conductors in the socket to the lugs disposed within the shell of the socket adapter.
The need for the above-described adapter is an example of a frequently encountered problem in the power metering industry which occurs whenever a watthour meter which is to be plugged into a watthour meter socket contains more blade terminals than the number of jaw terminals present in the socket. Watthour meters can have additional blade terminals for a number of different applications such as for use in remote pulse initiation, remote meter reading, ground connections, etc. When it becomes necessary to use such a watthour meter in an existing socket, extensive modifications to the socket are necessary to add jaw terminals to receive the additional blade terminals on the watthour meter. Besides the inconvenience of the interruption of power to the customer while such modifications are being made to the socket, such modifications can be so extensive that a new socket is required.
Thus, it would be desirable to provide a watthour meter socket adapter which allows a watthour meter which has blade terminals not available in a socket to be used without extensive modification to the socket or the need for a new socket. It would also be desirable to provide such a watthour meter socket adapter which may be simply constructed without extensive modifications to conventional socket adapter construction. It would be desirable to provide a watthour meter socket adapter for converting three phase three wire electric utility service to three phase four wire service to a load distribution network which enables a watthour meter to measure power on all three line conductors. It would also be desirable to provide such a watthour meter socket adapter which provides a simplified connection to existing watthour meter socket third line and load conductors.